Manufacture of dyestuffs



Reissued Mar. 9, 1948 MANUFACTURE OF DYESTUFFS Norman Hulton Haddock,Blackley, Manchester,

England, assignor to Imperial Chemical Industries Limited, a corporationof Great Britain No Drawing. Original No. 2,368,658, dated February 6,1945, Serial No. 443,670, May 19, 1942. Application for reissueSeptember 17, 1947, Serial No. 774,663. In Great Britain May 23, 1941 8Claims. 1

The present invention relates to the manufacture of dyestuils andintermediates therefor.

According to the invention I tetrazotise a diamino-p p'- di-(fi-methylbenzthiazyl) azobenzene which has been made as describedbelow, and cause the resulting tetrazo compound to react with an alkylxanthate or an alkali metal thiccyanate, thereby obtaining thecorresponding dixanthatoor dithiocyano-p:p'-di-(6-methylbenzthiazyl)azobenzene.

The invention also comprises the step of hydrolysing a dixanthatoordithiocyano-p:p-di- (fi-methylbenzthiazyl) azobenzene obtained in theabove manner, to the corresponding dimercaptop:p'-d1-(6methylbenzthiazyl) azobenzene and oxidising the latter to thecorresponding polydisulphide.

The present polydisulphides represent sulphurc-ontaining dyestufis whichmay be applied to cellulosic material from sodium sulphide according tothe usual practice with sulphur dyestufis. By this means there areobtained bright orange-yellow shades possessing excellent fastness tosevere washing, chemick and light.

The dixanthato and dithiocyano derivatives of p:p'-di-(6methylbenzthiazyl) azobenzene referred to above, not only constituteintermediates in the described manufacture of sulphur-containingdyestuffs, but may themselves be applied to cellulosic material fromsodium sulphide solution according to the usual practice with sulphurdyestufi's. By this procedure the dixanthato and dithiocyano derivativesbecome hydrolysed in the sodium sulphide solution to the correspondingdimercapto derivatives. The latter subsequently become oxidised topolydisulphides on the fibre. Thus by the dyeing technique commonlyemployed with sulphur dyestuifs there are produced on the fibre the samesulphur dyestulis, to the production in substance of which the above-mentioned processes relate. In this way also, dyeings are obtained havingthe properties already described.

Accordlngly, this invention is to be regarded as relating not only tothe manufacture by the aforesaid processes of sulphur-containingdyestuffs in substance, but also to their production on the fibre, thatis on the cellulosic material directly, by employing in the techniqueusual in dyeing with sulphur dyestuffs, the above intermediate products,namely the dixanthato and dithiocyano derivatives ofp:p-di-(6-methylbenzthiazyl) azobenzene.

The starting material which is a diamino p:p' di-(fi-methylbenzthiazyl)azobenzene, is made either (a) by oxidising nitro-dehydrothio-pto1uidine(nitro 6 methyl-Z-p-aminophenylbenzthiazole see German specification No.81,711) for example, in solution in ethylene glycol monoethyl ether withsodium hypochlorite, and reducing the resulting dinitro-p :p-di-(G-methylbenzthiazyl) azobenzene with e. g. sodium sulphide, or (b) bynitrating p p -di- (ii-methylbenzthiazyl) 'azobenzene, obtained by theoxidation of dehydrothio-ptoluidine, and reducing thedinitro-p:p'-di-(6- methylbenzthiazyl) azobenzene thus obtained.

By alkyl xanthate (also tobe referred to as alkyl xanthogenate or alkoxydithioformate) I mean a salt of an alkyl derivative of xanthic orxanthegenic acid, for example, the ethyl derivative. The latter itselfis often called more briefly xanthic or xanthogenic acid. Thus, I mayemploy, for instance, as alkyl xanthate, potassium ethyl xanthate orxanthogenate or potassium isopropylxanthate. As an alkali metalthiocyanate there may be used in accordance with the invention, forexample, sodium or potassium thiccyanate.

The following examples in which the parts are by weight illustrate butdo not limit the invention.

Example 1 16 parts of diamino-p1p-di-(6-methylbenzthiazyDazobenzene(made as described below) are dissolved in 230 parts of concentratedsulphuric acid at 29 C. A solution of 4.8 parts of sodium nitrite inparts of concentrated sulphuric acid is added and the mixture stirred at20 C. for hour. The resulting solution is now poured on to 950 parts ofa mixture of ice and Water, 10 parts of sodium thiocyanate dissolved inthe minimum quantity of water are added and the mixture is stirred andheated up to C. during hour. The temperature is maintained at 80-90 C.for a further hour. The yellow product in suspension is then filteredofi and washed free from acid. When dry, the dithiocyano-p p -di- (6-methylbenzthiazyl) azobenzene so obtained forms a yeilow powder whichis insoluble in water but dissolves in sulphuric acid with a red color.It may be used to dye cotton in a similar manner to the polydisulphidedescribed below.

The above dithiocyano-p:p'-di- (6-methylbenzthiazyl) azobenzene isdissolved in e00 parts of alcohol containing 40 parts of sodium sulphide(crystals). The solution is boiled for hour and diluted with 600 partsof water. The dithic cyano compound becomes thereby hydrolysed to thecorresponding dimercapto compound. 209 parts of sodium chloride areadded and the also hol is then distilled ofi. An orange yellowpreclpitate consisting of polydisulphide separates. The latter is formedby oxidation of the mercapto compound by dissolved atmospheric oxygen.The precipitate is filtered ofi and dried in air. It forms anorange-yellow powder which is insoluble in water but dissolves inaqueous sodium sulphide, preferably containing a little alcohol orglycerol, to yield a yellowish brown solution. Cotton is dyed by thissolution in shades which, after exposure to the air, are bright orangeyellow and possess excellent fastness to severe washing, chemick andlight.

The diamino-p :p'-di- (6-methylbenzthiazy1) azobenzene employed above,is made as follows. 20 parts of nitrodehydro-p-toluidine are dissolvedin 700 parts of boiling ethylene glycol monoethyl ether. The solution iscooled to 40 C. and 100 parts of sodium hypochlorite solution (13%available chlorine) are slowly added with good agitation at 40-45 C. Theyellowish brown precipitate of dinitro-p :p'-di- (G-methylbenzthiazyl)azobenzene is filtered off, washed with alcohol and dried. The saiddinitro compound is then stirred up with 600 parts of water containing120 parts of sodium sulphide (crystals) and boiled for 2 hours. Theproduct in suspension is filtered off, washed with water and then withalcohol and dried to a brown powder consisting of diaminopzp' di (6methylbenzthiazyl)azobenzene. This compound is insoluble in water andmineral acids but dissolves in concentrated sulphuric acid to a redsolution.

Example 2 3.3 parts of diamino-p:p-di-(6-methylbenzthiazyl) azobenzene(made as described in Example 1) (in the form of a 6.64% aqueous paste)and 110 parts of 10% aqueous sodium nitrite are cooled to 5 C. and addedslowly with stirring to 50 parts of 36% hydrochloric acid at C. Thetemperature is maintained at 0 C. during the addition. The mixture isstirred at 0 C. for A1. hour and poured into an equal volume of amixture of ice and water. The diazonium compound in suspension is nowadded slowly with good stirring to a solution of 10 parts of potassiumethyl xanthate and 20 parts of sodium carbonate in 200 parts of water at60 C. During the addition, further amounts of sodium carbonate are addedas needed in order to keep the solution alkaline to Brilliant Yellowpaper. The suspension is stirred at room temperature for 1 hour and thenat 80 C. for hour. The precipitate is filtered ,ofi', washed with waterand acetone and dried at 80 C. It is a brown powder soluble in dilutesodium sulphide solution.

The above product (dixanthato-p:p'-(S-methylbenzthiazyl) azobenzene) ishydrolysed by boiling with 50 parts of alcohol and 5 parts of sodiumsulphide (crystals) for hour. The resulting brown solution ofdimercapto-p:p'-di-(6- methylbenzthiazyl) azobenzene is diluted with 200parts of water and filtered from a trace of insoluble material. Thesolution is then boiled and the aforesaid dimercapto compound oxidised,by the addition of sodium m-nitrobenzene sulphohate, to give thecorresponding polydisulphide. The latter is thrown down as a brownprecipitate, the remaining liquor, when sufiicient sodium m-nitrobenzenehas been added to complete the oxidation, having turned from brown topale yellow. (The color of the liquor is conveniently seen by spottingon filter paper and examining the runout.) The brown precipitate is thenfiltered off and washed with water.

Both the dixanthato compound and the polydisulphide derived from it dyecotton in yellowish orange shades from boiling aqueous sodium sulphidesolutions. The shades so-obtained possess very good fastness propertiesparticularly in respect of severe washing and chemick.

Example 3 3.3 parts of diamino-p:p'-di- (G-methylbenzthiazyl) azobenzene(made as described in Example l) are diazotised with 11 parts of 10%aqueous sodium nitrite'as described in Example 2. The suspension of thediazonium compound soobtained is added slowly with stirring to asolution of 10 parts of potassium isopropyl xanthate and 20 parts ofsodium carbonate in 200 parts of water at 60 C. Sodium carbonate isadded as needed to keep the solution alkaline to Brilliant Yellow paper.The suspension is stirred at room temperature for 1 hour and then at C.for 4 hour. The precipitate(di-isopropylxanthatop:p-di-(6-methylbenzthiazyl) azobenzene is filtered off, washed with water and acetone and dried at 80 C. It is abrown powder soluble in boiling dilute sodium sulphide solution.

The above diisopropylxanthato compound is boiled with 50 parts ofalcohol and 5 parts of sodium sulphide (crystals) for hour. Theresulting brown solution of the corresponding dimercapto compound isdiluted with 200 parts of water, and oxidised with sodium m-nitrobenzenesulphonate and the polydisulphide isolated in the manner described inExample 2.

Both the diisopropylxanthato compound and the polydisulphide dye cottonin yellow shades from sodium sulphide solutions, of very good fastnessproperties.

Example 4 4.15 parts of diamino-p:p'-di-(6-methylbenzthiazyl) azobenzene(made as described below) in the form of an 8.3% aqueous paste arediazotised with 10% aqueous sodium nitrite as described in Example 1 andthe mixture then diluted with an equal volume of a mixture of ice andwater. 10 parts of sodium thiocyanate dissolved in 10 parts of water areadded and the mixture is stirred at 80 C. for half an hour and at 80-90C. for a further half hour. The brownish yellow precipitate ofdithiocyano-p:p'-di-(6- methylbenzthiazyl)azobenzene is filtered '05 andwashed with water until free from acid. It dyes cotton in yellow shadesfrom aqueous sodium sulphide solution, the shades having excellentfastness to washing and chemick.

The diamino-p:p-di- (G-methylbenzthiazyl) azobenzene employed above ismade as follows: 9.7 parts of ptpf-di-(S-methyibenzthiazyl)azobenzeneare dissolved in 55 parts of sulphuric acid (monohydrate) at 25-30 C.and 6.8 parts of potassium nitrate added slowlyin small quantities, thetemperature being maintained at 25-30" C. After stirring for 2 hours thetemperature is raised to 60-65 C. and maintained for 2 hours. Thesolution is then poured onto ice and the precipitated dinitro' compoundfiltered off andwashed with water. The so-obtained dinitrop:p'-di-(B-methylbenzthiazyl) azobenzene is reduced to the corresponding diaminocompound by boiling with 300 parts of water and '60 parts of sodiumsulphide (crystals) for 2 hours. When cool the brown product insuspension is filtered off, washed well with water and dried.

Example 5 4.15 parts of diamino-p:p'-di-(G-methylbenzthiazyl) azobenzenemade as in Example 4 in the form of an 8.3% aqueous paste are diazotisedwith 11 parts of aqueous sodium nitrite as described in Example 2. Themixtureis diluted with an equal volume of a mixture of ice and water andadded slowly with stirring to a solution of 10 parts of potassium ethylxanthate and parts of sodium carbonate in 200 parts of water at 60 C.Sodium carbonate is added as needed to keep the mixture alkaline toBrilliant Yellow paper. After stirring for 1 hour, the suspension isheated at 70 C. for 10 minutes, filtered and washed with water. Theproduct (dixanthatoin which X is one of a group consisting of thincyanoand alkali-metal alkyl-xanthato, with sodium sulfide and water in aninert liquid organic 10 wherein X is alkali-metal isopropyl-xanthato.

5. The process of making sulfur dyes which comprises heating asymmetrical compound represented by the formula in which X is one of agroup consisting of thio- 20 cyano and alkali-metal alkyl-xanthatowherein pound in aqueous medium with an oxidizing agent until thecorresponding polydisulfide is formed.

6. The process in accordance with claim 5 in which the organic solventis alcohol.

'7. The process in accordance with claim 5 in which oxygen is theoxidizing agent.

8. The process in accordance with claim 5 in CHI 40 which m-nitrobenzenesulfonate is the oxidizing agent.

NORMAN HULTON HADDOCK.

